This invention relates to slide fasteners well adapted for unopenably closing openings in upholstery coverings of chairs, sofas and like articles, among other applications. More specifically, the invention is directed to improved means for semipermanently locking a slider in its closed position on interlocking rows of fastener elements or scoops to prevent any accidental or undesired opening of the fastener.
The slide fasteners heretofore employed for the application in question have usually been provided with sliders of the automatically locking or cam-locked type, such that the sliders, when moved to their closed position on the interlocking rows of fastener elements, are locked against movement in the fastener opening direction by the built-in lock mechanism. These sliders, however, have originally been developed for use on fasteners applied to plackets and other closure openings in garments, bags and the like. In the sliders of both known types, a locking pawl is provided which is actuated by the pull tab into and out of engagement with the fastener elements in the guide channel of the slider body.
The slide fasteners incorporating such locking sliders are therefore readily openable, after having been closed, by manipulating the pull tabs of the locked sliders in the usual manner. When such fasteners are applied to openings in upholstery coverings of chairs and the like, they may be opened, for example, by children out of curiosity. This is undesirable because then the rubber sponge or like filling material within the coverings can be easily taken out.
The use of the locking sliders is also objectionable from an economic point of view, since they are significantly more complex and therefore more expensive than the usual non-locking type. It is indeed unnecessary to use such expensive locking sliders because the fasteners applied to openings in upholstery coverings need almost never be opened when once closed.